Sliding sleeve valves are used to regulate formation flow into a production string or to balance flows from an interval. The housing has a port as does a sliding sleeve that can move axially within the housing. Normally the sleeve has a series of circumferentially spaced slots that travel past an isolation seal to initiate formation flow into the production tubing. The initial flow has to rush past the seal that is uphole from the housing inlet port. High initial velocities can damage the seal so that in the past diffusers have been used to protect the seal by reducing the fluid velocity that reaches the seal.
One attempt to slow down the fluid velocity has been to use a non-metallic ring, primarily made of PEEK and place the ring upstream from the seal being protected. The problem with such designs is that the material had service limits and the high velocity gas and temperatures in many applications limited the service life of such designs. Such single rings are illustrated in U.S. Pat. No. 6,722,439 as item 38. They were typically installed in an interference fit to the sliding sleeve on the inside and the valve housing on the exterior side. Other sliding sleeve valve designs that have similar components are U.S. Pat. Nos. 7,363,981; 7,921,915 and 7,575,058.
Metal ring diffusers were also used as alternatives to the PEEK designs. The problem with these rings is that they needed too much clearance for mounting purposes and let too much flow at high velocity get to the seal.
What is needed and addressed by the present invention is a diffuser assembly that has the durability feature with the ability to slow or stop the incoming high velocity fluid before it can reach the seal assembly and damage the seal. Thus an assembly of rings is provided that is energized by differential pressure to enhance an initial fit that is at least a clearance fit but preferably is an interference fit to the sliding sleeve on the inside and the surrounding housing on the outside. The rings are fabricated with a bias either toward the sleeve or the surrounding housing and are preferably disposed in alternating arrangements. Sloping surfaces are used in conjunction with pressure differential to further bias some rings inwardly and adjacent rings outwardly. In another variation the rings are split and matched in pairs that are biased out alternating with pairs biased to move in. The rings that move in a given direction can be split with the splits offset circumferentially and the relative position of the adjacent rings that move in a given direction prevented from relative rotation using a projection on one ring registering with a depression on an adjacent ring for each pair of rings that are designed to move either inwardly toward the sleeve or outwardly toward the surrounding housing. These and other features of the present invention will be more readily understood by those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.